Authors: R.E. Cavicchi, D.C. Meier, C. Presser, S. Guha
Affilation: National Institute of Standards and Technology, United States
Pages: 382 - 384
Keywords: gold, nanoparticle, nanosphere, laser ablation, DLS, ES-DMA
Methods continue to be developed for improving the size and shape uniformity of Au nanoparticles (NP), however, fabricated NPs tend to be faceted and not highly spherical. We present results that show that the faceted NPs from a commercial gold colloid can be converted to highly spherical Au NPs by exposing the colloid to a single 7 ns pulse from a laser. Laser exposures were performed with a Q-switched Nd:YAG laser, with the 1064 nm line frequency doubled to produce a 532 nm beam, and a beam diameter of 4 mm. Nominally monodispersed colloids with diameters of 10 nm - 100nm were used. TEM results showed that for moderate fluence of the pulse, highly spherical NPs are formed as a result of the melting and resolidifying. Dynamic Light Scattering shows a tightening of the size distribution for the peak at the particle size. Some debris particles of <10 nm size are evident, but may be filtered or eliminated by further optimization of pulse conditions. This work also suggests that a simple laser pulse treatment may be useful for modifying coatings on NPs, or altering alloy NPs.